ABSTRACT: The detrimental effects of aging on auditory temporal processing have been well documented in humans and animal models. At present, there are gaps in knowledge of the extent to which these auditory tem- poral processing deficits can be mitigated in older adults with or without hearing loss through auditory training and neuroplasticity, to improve precision of neural timing and speech understanding. Our long-term goal is to determine the extent to which hearing deficits in older adults can be ameliorated with auditory training. We pro- pose an innovative approach to the investigation of aging, hearing, and neuroplasticity by marrying perceptual training experiments with electrophysiological measurements. The objectives are to compare young normal- hearing (YNH), older normal-hearing (ONH), and older hearing-impaired (OHI) adult listeners, and evaluate the improvements in perceptual and electrophysiological measures of temporal processing after explicit training on auditory temporal processing tasks. Our central hypothesis is that training of auditory temporal processing will produce concomitant improvements in both perceptual performance and neural encoding, which will close the gap in the age-related differences between groups. With strong preliminary data in hand, the central hypothesis will be tested by pursuing three specific aims: (1) Determine the extent to which perceptual training on temporal rate discrimination using simple non-speech stimuli improves perceptual and neural encoding in YNH, ONH, and OHI listeners; (2) Determine the extent to which perceptual training on speech cue discrimination in contrasting words differing in discrete temporal cues improves perceptual and neural encoding in YNH, ONH, and OHI lis- teners; and (3) Determine the extent to which perceptual training on the processing of sentences with increasing presentation rate can improve behavioral performance and neural encoding in YNH, ONH, and OHI listeners. The expected outcomes are that we will learn what perceptual training tasks lead to simultaneous improvements in perceptual and neural auditory temporal processing and the findings will produce a significant impact in older listeners who experience difficulty in communicating in daily life because they will lead directly to focused and novel forms of rehabilitation. This research is innovative because we will have established techniques that are proven to provide significant improvements in auditory temporal processing and speech perception, combined with evidence of improvements to neural encoding. These studies will serve the larger goals of the program project grant because they will help identify the neuroplastic mechanisms in the brain of humans that correspond to successful behavioral outcomes in younger and older adults